Biomass waste conversion into low-cost carbon-based materials for supercapacitors: A sustainable approach for the energy scenario

Biomass upgrading is a promising approach to face the current energy consumption and chemicals production. Lignocellulosic biomass residues have taken the lead in this field. In this study, hemp residue-based activated carbons (ACs) were prepared by H3PO4-assisted hydrothermal carbonization (HTC) using a low concentration of H3PO4 (25 wt%). ACs with a high porosity development were obtained (SBET > 1200 m2 g−1), and they were subsequently functionalized with nitrogen groups using mild conditions. As-synthesized ACs were also heat-treated to enhance the electrical conductivity, improving the electrochemical performance. As a proof of concept, electrochemical capacitors (ECs) based on as-prepared ACs in aqueous and organic electrolytes, showing energy densities comparable to those of a capacitor based on an AC used in commercial capacitors. The most attractive outcome of this study is the straightforward, cost-effective, and sustainable methodology to prepare high added-value functional ACs with great potential for energy and environmental applications. [Display omitted] •High yields of biomass waste upgrading compared those of traditional methods.•Cost-effective and sustainable carbon materials.•High performance N-doped ACs were prepared from a hemp residue.•An efficient use of energy through electrochemical storage devices.•N-doped ACs-based supercapacitors with high efficiency and stability.